Webb has been in excellent form for Leeds this season
New Zealand and Leeds full-back Brent Webb has been ruled out of the World Cup after undergoing spinal surgery to correct a long-standing back injury.
The 27-year-old could be out of action for up to six months, which would rule him out of the start of next year's Super League season.
Webb, who missed last week's Grand Final, will be replaced in the 24-man World Cup party by Jason Nightingale.
Melbourne prop Jeff Lima (knee) is also out and is replaced by Evarn Tuimavave.
New Zealand Warriors front rower Tuimavave, 24, who has 99 NRL appearances to his name, has yet to play for the Kiwis but was in the 19-man squad in Brisbane for last year's Anzac Test against the Kangaroos.
"We've been in touch with both Brent and Jeff and they're obviously devastated," said coach Stephen Kearney.
"Webby's situation wasn't looking too good but we all remained hopeful awaiting a final decision."
Forward Sika Manu is the only newcomer in the squad.
Nightingale, 22, who plays wing or full-back for St George Illawarra, will face competition for Webb's number one jersey from Lance Hohaia, Krisnan Inu and Sam Perrett.
"While we lose Webby, we still have plenty of options at full-back, and that hasn't always been the case with Kiwi teams in recent years," added Kearney.
"Lance was great there for the Warriors this year, Sam and Krisnan both played at full-back for the Kiwis last year and Jason can also cover the position."
And Kearney is delighted with the strength of the squad, saying: "We've got a lot of players who have been involved in finals football in the NRL and the English Super League, so that's a real positive.
"What we do have is more options than Kiwi teams have had for some time in the key positions of full-back, in the halves and hooker."
But his squad will undoubtedly be weaker for the absence of Webb, while Manly's Steve Matai is an injury doubt with ongoing neck and shoulder concerns.
Webb has struggled with the back injury in recent months, and his club side are hopeful the surgery will repair the problem in the long term.
Leeds head physiotherapist Meirion Jones said: "It is hoped that the surgery will clear up Brent's current symptoms.
"However, the key will be a sustained period of five to six months rehabilitation to compliment the surgery to get Brent back to full fitness."
Kearney will also be without Sonny Bill Williams, who has defected to rugby union, while his first-choice captain Roy Asotasi and Frank Pritchard are both injured.
"Losing any one of those three players is a big miss, so losing all three is fairly big," added Kearney, who has handed the captaincy to Parramatta's Nathan Cayless.
"We are lucky to have a lot of depth in the forwards though and I am sure that the forwards we do pick will do a good enough job for us.
"There are a lot of players that I am looking forward to working with and I know that if we prepare as we should do, then we will be fine."
The World Cup starts in Australia on 25 October.
New Zealand are in a group with holders Australia, England and Papua New Guinea, with three teams making it through to the semi-finals.
New Zealand: Nathan Cayless (Parramatta, capt), Adam Blair (Melbourne), Greg Eastwood (Brisbane), David Fa'alogo (South Sydney), Nathan Fien (NZ Warriors), Dene Halatau (Wests Tigers), Lance Hohaia (NZ Warriors), Krisnan Inu (Parramatta), David Kidwell (South Sydney), Thomas Leuluai (Wigan), Jeff Lima (Melbourne), Isaac Luke (South Sydney), Simon Mannering (NZ Warriors), Sika Manu (Melbourne), Benji Marshall (Wests Tigers), Steve Matai (Manly), Sam Perrett (Sydney Roosters), Sam Rapira (NZ Warriors), Jerome Ropati (NZ Warriors), Setaimata Sa (Sydney Roosters), Jeremy Smith (Melbourne), Iosia Soliola (Sydney Roosters), Manu Vatuvei (NZ Warriors).